树视图WPF错误26 ItemTemplate和项模板选择器将被忽略

Question

我有以下代码将项目附加到树视图，MyTreeViewItem是一个继承自TreeViewItem的自定义类：

        foreach (
            Site Site in
            SiteManager.SiteList.ToList()){

            MyTreeViewItem    HistoricalItem        = new MyTreeViewItem();

            HistoricalItem.LeftHeader.Content = Site.Profile.Username;
            HistoricalItem.BtmSubHeader3.Content = String.Format("Total: {0, 8:N0}", Site.Total);


            HistoricalItem.ItemsSource = Site.HistoricalList;
            HistoricalTree.Items.Add(HistoricalItem);

        }

以及以下相关的XAML代码::

    <DataTemplate x:Key="HistoricalTemplate">
        <StackPanel Orientation="Horizontal">
            <Label 
                Content="{Binding Path=Timestamp}"
                FontFamily="Consolas"
                Width="80" 
                HorizontalContentAlignment="Right" 
                VerticalContentAlignment="Center"
                Height="30"/>
            <Label 
                Content="{Binding Path=HeaderText}" 
                FontFamily="Consolas"
                Width="500" 
                HorizontalContentAlignment="Left" 
                VerticalContentAlignment="Center"
                Height="30"/>
            <Label 
                Content="{Binding Path=Total}" 
                FontFamily="Consolas"
                Width="250" 
                HorizontalContentAlignment="Right" 
                VerticalContentAlignment="Center"
                Height="30"/>
        </StackPanel>
    </DataTemplate>

                <TreeView ItemsSource="{Binding }"
                          ItemTemplate="{StaticResource HistoricalTemplate}" 
                          Margin="0,10,0,0" 
                          Name="HistoricalTree" 
                          Background="{x:Null}" 
                          BorderBrush="{x:Null}" 
                          FontFamily="Consolas" 
                          FontSize="12">

                </TreeView>

现在的问题是，当我运行这个程序时，模板实际上没有应用，我得到错误26：ItemTemplate被忽略。我不确定为什么被忽略或如何解决它。有任何想法吗？